Adjustment means for electrical switch



C. N. JOHNSON ADJUSTMENT MEANS FOR ELECTRICAL SWITCH April 16, 1968Filed Jan. 3, 1966 mgr M a m m m M m 3 a l/ 4 2 4 x 1 2 2 2 m F M m CARLN. JOHNSON,

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United States Patent 3,378,656 ADJUSTMENT MEANS FOR ELECTRICAL SWITCHCarl N. Johnson, Braintree, Mass assignor to Texas InstrumentsIncorporated, Dallas, Tex., a corporation of Delaware Filed Jan. 3,1966, Ser. No. 518,404 8 Claims. (Cl. 20083) ABSTRACT OF THE DISCLOSUREElectrical switches are shown with improved means for adjusting thesnap-acting characteristics of a snap-acting diaphragm. An exemplarypressure responsive electrical switch is shown having upper and lowercasing members provided with cavities which are hermetically sealed fromone another by a snap-acting diaphragm mounted therebetween. One cavityadmits pressure to one side of the diaphragm while the other cavityhouses an electrical switch which is actuated in response to movement ofthe diaphragm. The adjustment of the pressure differential of thesnap-acting diaphragm is such that it can be effected without affectingthe hermetic seal. In one embodiment the diaphragm is mounted on aflexible annular ring which cooperates with a threaded annular memberwhich can be moved upwardly to stress and bend the flexible annular ringand hence the peripheral portions of the diaphragm which results inchanging of the pressure differential of the diaphragm.

Another embodiment shows the peripheral portion of the diaphragmprojecting axially beyond the casing members and mounted betweenflexible ring flanges of the casing members. A force can be directlyapplied to the ring flanges to thereby bend the projecting peripheralportion of the diaphragm. A way of applying a force to the ring flangesis shown employing threaded rings which are movable to bring abutmentson the rings into pressure engagement with the ring flanges to bend theflanges and projecting peripheral portions of the diaphragm. The casingmembers are shown to be cylindrical in configuration however could bevaried to include rectangular, octagonal or other polygonal shapes.

This invention relates generally to electrical switches, and, moreparticularly, to pressure responsive devices adapted for actuatingelectrical switches and the like.

Among the several objects of the invention is the provision of apressure responsive device which is particularly adapted forminiaturization and for lightweight, hermetically sealed and openconstruction and which is capable of sensing relatively wide ranges ofvalues in pressure, which has a high degree of sensitivity and iscapable of operating within a relatively narrow range of pressurevalues.

It is a further object of the invention to provide such a pressureresponsive device in which adjustment of the magnitude of the pressuredifferential of the device can be easily achieved without deleteriouslyaffecting the resistance of the device to vibration or without affectingits sensitivity.

Other objects will be in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction and arrangements of parts which willbe exemplified in the structure hereinafter described and the scope ofthe application of which will be indicated in the appended claims.

In the accompanying drawings in which several of the various possibleembodiments of the invention is illustrated,

FIG. 1 is an elevational view partly in section of a device according tothe instant invention;

FIG. 2 is an enlarged view of a portion of the device shown in FIG. 1;

FIG. 3 is a view similar to FIG. 1 of a second embodiment of a deviceaccording to the instant invention; and

FIG. 4 is an enlarged view of a portion of the device showing a thirdembodiment of the device shown.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Dimensions of certain of the parts as shown in the drawings may havebeen modified or exaggerated for the purposes of clarity ofillustration.

In devices of the type contemplated by the instant invention, it isfrequently desired to open or close an electrical circuit or operate anelectrical switch in response to changes in the values of pressure andthis is accomplished by admitting pressure to one side of a snap actingdiaphragm which will snap move from one position to another at apredetermined value of pressure and return to its original position atanother value of pressure. The difference between these pressure valuesis called the pressure differential of the diaphragm of the device. Itis frequently desired to alter the magnitude of this differential tonarrow or widen it and thereby to vary its sensitivity. It is desirableto perform this variation without altering the magnitude of the movementof the snap acting diaphragm, since this may deleteriously affect thestability of the position of the diaphragm and hence of the deviceswhich it is set to operate. It has been found that by altering the slopeof the peripheral portion of the snap acting diaphragm such anadvantageous differential adjustment can be achieved.

Referring now to the drawings, particularly FIG. 1, there is shown anexemplary pressure responsive device generally designated by referencenumeral 10. Pressure responsive device 10 includes upper and lowercasing members 12 and 14 respectively which may be formed of materialhaving suitable strength and corrosion resistance such as, for example,stainless steel. Casing member 14 is provided with a peripherallyextended flange 16 which is aligned with a lower portion of casingmember 12 to permit positioning of the casing members in telescopedrelationship as shown in the FIG. 1 and to permit joining as, forexample, by welding at 18.

As seen in FIG. 1, casing member 14 includes mounted on an inner portionthereof between casing 14 and casing 12, a flexible ring member 2%). Theinner peripheral portion 21 of member 20 projects radially inwardlybeyond the portion of casing 14 on which it is mounted to create anoverhang or freely movable portion. Mounted on ring 20 as, for example,by welding at the radial periphery of the ring is a diaphragm member 22which includes a deformed portion 23 which is responsible for its snapmovement between the solid line position and the dotted line positionshown in FIG. 1.

In the assembled form shown in FIG. 1, casing members 12 and 14 providecavities or compartments 28 and 123, respectively which are hermeticallysealed from one another by the welding of diaphragm 22 to ring 20 and ofring 20 to housing 14. It will be understood that other means thanwelding may be employed to clamp and seal.

Casing member 12 has formed thereon a mounting member 31 which includesan orifice or port 24 which communicates with the interior ofcompartment 28 and which serves as an inlet to admit a source ofpressure to which diaphragm member 22 is to respond.

There is a critical force of a predetermined value which when exerted ondiaphragm 22 will cause snap movement of member 22 toward the dottedline position from the solid line position of FIG. 1.

In the diaphragm construction shown in FIG. 1, the deformed portion 23is responsible for this snap movement. In general the degree ofdeformity of portion 23 determines the magnitude of the force requiredto actuate member 22.

In addition, the value of the pressure required for actuation may bevaried by providing a spring member (not shown) within aperture 24, oneend of which is fixed and the other end of which bears against deformedportion 23 to alter the magnitude of the pressure required for actuationas disclosed and claimed in co-pending U.S. patent application Ser. No.317,338, filed in the name of Carl N. Johnson on Oct. 18, 1963 andentitled Condition Responsive Devices and assigned to the assignee ofthe instant invention. In addition, this value may be altered by varyingthe number of diaphragms employed as shown in FIG. 3.

Preferably, diaphragm member 22 is formed of a relatively thin,corrosion-resistant, strong material such as, for example, stainlesssteel and is in the form of a disc of substantially uniform thickness.It will be noted that the peripheral portion 25 of diaphragm member 22is substantially undeformed and lies in a plane along the flexibleannular ring member 20 which is mounted on the inner portion of casing14.

Received in threaded engagement on the interior of the cavity formed bycasing member 14 is an annular ring member 26 on which rests a wallportion 27 which, together with the diaphragm 22 divides cavity 123formed by casing member 14 from cavity 28 formed by casing 12. Receivedwithin a central aperture 30 in wall portion 27 is a motion transfer pin31 formed of electrical insulating material, the upper end of whichbears against the deformed portion 23 of diaphragm member 22 and thelower portion of which bears against a switch mechanism generallydesignated by reference numeral 100.

Exemplary switch 100 is substantially identical to that described inco-pending application Ser. No. 317,338, filed in the name of Carl N.Johnson, entitled Condition Responsive Devices and assigned to theassignee of the instant invention now abandoned in favor of continuationapplication Ser. No. 575,194, filed Aug. 25, 1966, which issued asPatent No. 3,335,242 on Aug. 8, 1967 and also described in copendingapplication Ser. No. 432,067, filed in the name of Lawrence E. Cooperand Edmunds Kadisevskis and assigned to the assignee of the instantinvention. Other exemplary mechanisms actuable by the pressureresponsive device include the several other switch species disclosed inthe above application of Copper et al. as well as the so-called W-bladeswitch mechanism disclosed in Us. Patent No. 2,777,032, dated Jan. 6,1957 and the overcentering switch shown and described in copendingapplication Ser. No. 518,360, filed Jan. 3, 1966, entitled Snap ActingOvercentering Means for Electrical Switches, in the name of Carl N.Johnson and assigned to the assignee of the instant invention issued asPatent N0. 3,322,915 on May 30, 1967.

As seen in FIG. 1, casing member 14 includes cupshaped recess or cavity123 suitable for the reception of switch 100 which includes a metallicheader plate 102 mounted in sealing relationship on bushing 14 at 15.Header 102 includes open-ended apertures 104 in which are respectivelydisposed and hermetically sealed relationship, electrically conductiveterminals 108 and 110 and about which is disposed glass sealant 112 tohermetically seal and maintain terminals 108 and 110 in electricallyinsulated relationship with respect to the header 102. Where an openconstruction is desired, a phenolic header plate 102 may be employed.Terminal 108 has mounted at one end thereof an electrically conductivecontact 114. Switch 100 further includes an electrically conductivecontact-carrying spring member 116 which is electrically connected toand cantilever mounted adjacent one end thereof on a portion 118 ofterminal member 110 as shown. Spring member 116 carries an electricalcontact 120 adjacent the free end thereof which is positioned formovement into and out of engagement with stationary contact 114. Springmember 116 is moved from-the solid line posi- 4 tion to the dotted lineposition shown in FIG. 1 in response to movement of motion transfermember 31 and diaphragm member 22 from the position shown in FIG. 1 tothe dotted line position shown in FIG. 1. It can thus be seen that apressure suflicient to actuate member 22 will move contacts and 114 intoand out of engagement.

Turning now to FIGS. 1 and 2, it can be seen that when ring member 26 isrotated Within the threaded portion of housing 14 as by a tool insertedin slot 29 the ring member 26 can be made to move up or down as viewedin FIG. 2 along a direction parallel to the direction of motion of thecentral portion 23 of diaphragm 22. When moved upwardly as shown in FIG.2, ring 26 engages the periphery of wall portion 27 which rests on itsand urges it upwardly until a peripheral portion of the wall 27 engagesthe inner end of flexible ring 20. Further movement of ring member 26moves flexible ring member 21 from the position shown in FIG. 1 to theposition shown in FIG. 2 which thus stresses and bends the peripheral ormarginal portion 25 of the diaphragm 22. Movement in the other directionreleases the ring 20 and marginal portion 25. This axial movement hasthe effect of narrowing or widening the pressure differential ofdiaphragm 22 depending on the direction moved. It will be noted thatthis variation of the pressure differential can be accomplished without,in any way, deleteriously affecting the movement of the diaphragm member22 which could deleteriously affect the contact pressure or the pressureof engagement of contact member 120 and 114 or could cause inadvertentopening and closing of the circuit in switch 10 by lowering the contactforces at or around the operating points. A further embodiment of thedevice is shown in FIG. 3 where wall 27 and the deformable ring portion20 are shown as formed integrally and together with the peripheralportion 25 of diaphragm member 22 which project beyond housing 12 and 14in an axial direction. It will be noted that casing members 12 and 14are formed with peripherally extending flanges 13 and 15 such that theflanges, the diaphragm periphery 25 and the flexible ring portion 20form a sandwich extending radially from the housing. It will be seenthat when this projecting marginal portion is engaged by forces tendingto deform or bend the peripheral portion 25 of the diaphragm 22 from thesolid line position to the dotted line position shown in FIG. 3, theadjustment of the pressure differential described above can beaccomplished. This embodiment has the added advantage of providing foradjustment of the switch without entering the hermetically sealedportion thereof. Alternatively, as shown in FIG. 4, the housing 12 and14 can be filled with threaded portions on which are mounted in threadedengagement ring portions 40 and 42 which have abutments 41 and 43respectively which engage the radially extended portion 25 of thediaphragm to permit bending thereof to effect the pressure differentialadjustment. Members 40 and 42 can be locked into adjusted position.

It will be understood that the housing members could alternatively bemade of phenolic material as desired. It will also be noted that casingmembers 12 and 14 while preferably cylindrical in configuration topermit diaphragm member 22 to be made of a complementary circular shapecorresponding to cylindrical configuration of the casing members, such across sectional configuration may be varied to include rectangular,octagonal or other polygonal shape. Threaded portion 34 of member 31permits a means of mounting or securing the pressure responsive deviceon a source of pressure which is to be sensed.

It will thus be seen that the objects of the invention are achieved.Thus, a pressure sensitive switch permitting compact,hermetically-sealed or open construction is provided whose differentialmay be adjusted without deleteriously affecting the operation of theswitch in a simple and inexpensive manner.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results are obtained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense, and it is also intended that the appended claims shall cover allsuch equivalent variations as come within the true spirit and scope ofthe invention.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of elementsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also, it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

I claim:

1. A pressure responsive device comprising first and second casingmembers resectively providing first and second cavities; a snap-actingdiaphragm positioned intermediate and permanently secured to aperipheral portion of at least one of said first and second casingmembers so that the diaphragm separates and hermetically seals the firstcavity from the second cavity; the diaphragm having a deformed portiontherein responsible for its snap action; an orifice provided by thefirst casing member communicating with the first cavity to admit fluidunder pressure against one side of said diaphragm to effect snapmovement of the diaphragm in a direction toward the second casingmember; means mounted and positioned on the second casing for actuationthereof in response to snap movement of said diaphragm; a motiontransfer member positioned intermediate the actuable means and thediaphragm to transmit snap movement of the diaphragm to the actuablemeans; and means mounted on one of said casing members adjacent theperipheral portion of the snap acting diaphragm, the means movable tobend the peripheral portionof said snap acting diaphragm and saidperipheral portion of said one casing member out of the plane of thediaphragm to modify the pressure differential of the snap actingdiaphragm.

2. A device as set forth in claim 1 wherein the peripheral portion ofthe snap acting diaphragm is mounted on one of the casing members, saidone of the casing members including a portion movable toward and awayfrom the peripheral portion of the snap acting diaphragm member andoperable to exert force on the peripheral portion of the diaphragmmember and the said one casing member to adjustably vary the pressuredifferential of the diaphragm.

3. A device as set forth in claim 1 wherein the diaphragm member ismounted on the second casing memher and said second casing memberincludes a threaded portion on which is mounted in threaded engagementat ring member operable to exert a force on flexible portions of theperiphery of the snap acting diaphragm to effect adjustable variation ofthe pressure differential of the diaphragm.

4. A device as set forth in claim 1 wherein the peripheral portions ofthe snap acting diaphragm mounted on said portion of said one casingmember extends radially outward from the walls of the casing to permitbending of the peripheral portions of the snap acting diaphragmexteriorly of the casing to effect variable adjustment of the pressuredifferential of the snap acting diaphragm.

5. A device as set forth in claim 4 wherein the exterior of said one ofsaid casing members is threaded to receive a threaded ring; a threadedring mounted on the threaded casing member and including abutment meansthereon engageable with a peripheral portion of the snap actingdiaphragm to effect movement thereof to adjust the pressuredifferential.

6. A device as set forth in claim 5 wherein the means responsive tomovement of the diaphragm comprises an electrical switch including acontact-carrying arm having a contact thereon capable of movement intoand out of engagement with a stationary contact in response to movementof the motion transfer member to open and close a circuit betweencontacts.

'7. A switching device comprising a casing member defining a cavitytherein, a snap acting diaphragm permanently secured to a peripheralportion of said casing member to seal said cavity, said diaphragm havinga deformed portion therein responsible for its snap action, forceexerting means mounted on said casing member adjacent the peripheralportion of the diaphragm, the force exerting means movable to bend theperipheral portion of said casing member and the peripheral portion ofsaid snap acting diaphragm out of the plane of the diaphragm to modifythe snap acting characteristics of the diaphragm.

8. A device as set forth in claim 5 wherein the exterior of the other ofsaid casing members is threaded to receive a threaded ring; a secondthreaded ring mounted on the threaded exterior of the said other casingmember, the second ring including abutment means engageable with aperipheral portion of the snap-acting diaphragm at a point spacedradially inwardly from the outer peripheral edge of said diaphragm.

